P3A battery acting strange

[jimlips]

A little background - I've got two batteries on my P3A - the original that came with it, and one that I purchased brand new in March 2017. This newer one is the one in question. It has 67 charges, and was working fine. I took the aircraft for a flight yesterday, everything went fine with the battery. It still showed about 50% charge left. I wanted to calibrate my IMU when I got home, because the aircraft wasn't hovering level. I proceeded to complete the IMU calibration procedure (and did the compass, too). I thought it I would take it for a quick hover to make sure it worked, and while it was hovering, just a few feet off the ground, I got a "Battery critically low" warning on the RC, and it proceeded to land. I was lucky, it was over grass. My question is, what happened? How can it start out with a 50% battery, hover for 30 seconds, then have a "Battery critically low" alert? Is there a problem with my battery? Here is the Airdata info that flight (it shows all the battery info): Click on POWER, then CELLS GRAPH, you can see that the battery level plummeted after taking off near the middle of the graph.

 

[Offroader]

This is a commonly discussed issue on this forum. These batteries often behave strangely when used when not completely charged. It is a very good thing you were not at a significant altitude.

 

[Deleted member 62848]

How many lights come on when power pressed and held,could be bad cell or its given up,,,don't fly with it,,I had exact same with p4 batt,killed me drone,,if any doubt don't use it,,,it's just not worth losing your investment

 

[Oso]

This is a commonly discussed issue on this forum. These batteries often behave strangely when used when not completely charged. It is a very good thing you were not at a significant altitude.

Agreed. We've had so many people post here saying, "I was only planning a short flight and thought it would be enough," followed by something like, "it went to critical and now I don't know where it landed," or "and then it landed in the lake."

 

[Fly Dawg]

you can see that the battery level plummeted after taking off near the middle of the graph.

This is normal to see the voltage drop in this manner at takeoff. It will do this even with a fully charged battery. Notice your overall percentage did not change. It is the load on the initial takeoff that does this. That said, if the battery is not fully charged, the drop will reach the lower cell values which will trigger "critical battery".

 

[3rdof5]

Just to chime in, the rule of never taking off without a fully charged battery is the wisest rule. That being said, I have landed temporarily and took off again during one total flight without any battery issues. But a fresh flight, I always start fully charged.

 

[Quest-So]

Hi @jimlips In deed, at very low levels do fall all 4 cells after take-off.
Would you please fully charge this battery and fly with it just by hovering at 2 m from ground till the battery reaches 20% ? Then share us again the link to AirData to see the Cells Graph.
It would be interesting to see its behaviour difference when discharging from 100%. Don't forget to switch on the battery before connecting it to the charger, to gain its 100% toping. Fly in the next hour after toping the battery. If not possible, top the battery before flying by charging it while it's switched on.

 

[fw190]

L

Hi @jimlips In deed, at very low levels do fall all 4 cells after take-off.
Would you please fully charge this battery and fly with it just by hovering at 2 m from ground till the battery reaches 20% ? Then share us again the link to AirData to see the Cells Graph.
It would be interesting to see its behaviour difference when discharging from 100%. Don't forget to switch on the battery before connecting it to the charger, to gain its 100% toping. Fly in the next hour after toping the battery. If not possible, top the battery before flying by charging it while it's switched on.

What do you mean,
Switch on battery before charging?
I have not seen this in any documentation on a phantom 3a!

 

[3rdof5]

L
What do you mean,
Switch on battery before charging?
I have not seen this in any documentation on a phantom 3a!

Sometimes charging stops at around 95%. Switching the battery on before connecting the charger allows it to charge to 100%

 

[Quest-So]

Neither did I @fw190 but many guru-pilots are recommending it. The battery has to be switched on prior connecting it to the charger. I have too a DJI Phantom 3 hub charger (4x). I haven't tryed this method while charging into this particular charger, but after the procedure completes I top each and every battery using the normally provided charger (I have a 0.7C model since initially I had a P3A).

 

[solentlife]

The switch on battery then charge is actually a routine for topping up a battery that is above 90% charged. If you do not switch on before plugging in charger - the charge control board will not allow battery to top up. You think battery is full but in fact its not.

Switching on battery before plugging in charger over-rides the default setting of the charge control board in the battery and allows a 100% charge to be accomplished.

I actually always switch on battery before charging - even from storage levels. All my flights then show 100% on take-off.

 

[fw190]

Sometimes charging stops at around 95%. Switching the battery on before connecting the charger allows it to charge to 100%

Thankyou 3rdof5 I will do in future as I would hate to be caught out loosing my machine.